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Friday, August 16, 2013

Process Description and Control Presentation Transcript:
1.Process Description and Control

2.Requirements of an Operating SystemInterleave the execution of multiple processes to maximize processor utilization while providing reasonable response timeAllocate resources to processesSupport inter process communication and user creation of processes

3.ConceptsComputer platform consists of a collection of hardware resourcesComputer applications are developed to perform some taskInefficient for applications to be written directly for a given hardware platformOperating system provides a convenient to use, feature rich, secure, and consistent interface for applications to useOS provides a uniform, abstract representation of resources that can be requested and accessed by application

4.Manage Execution of ApplicationsResources made available to multiple applicationsProcessor is switched among multiple applicationThe processor and I/O devices can be used efficiently

5.ProcessA program in executionAn instance of a program running on a computerThe entity that can be assigned to and executed on a processorA unit of activity characterized by the execution of a sequence of instructions, a current state, and an associated set of system instructions

7.Process Control BlockContains the process elementsCreated and manage by the operating systemAllows support for multiple processes

8.Process Control Block

9.Trace of ProcessSequence of instruction that execute for a processDispatcher switches the processor from one process to another

10.Example Execution

11.Two-State Process ModelProcess may be in one of two statesRunningNot-running

12.Not-Running Process in a Queue

13.ProcessesNot-runningready to executeBlockedwaiting for I/ODispatcher cannot just select the process that has been in the queue the longest because it may be blocked

14.A Five-State ModelRunningReadyBlockedNewExit

15.Suspended Processes is faster than I/O so all processes could be waiting for I/OSwap these processes to disk to free up more memoryBlocked state becomes suspend state when swapped to diskTwo new statesBlocked/SuspendReady Suspend